An outline is given of objective behaviour rating scales developed for use by nurse custodians in the maximum security hospital setting. Four independent scales are described: (a) antisocial belligerence, (b) disorientation, (c) withdrawal and (d) personal hygiene. The scales gave high test-retest and inter-rater reliabilities. Various indications of validity and potential usefulness of the scales are given. In particular, a probable relationship of the scales (a) and (c) with an impulsivity/overcontrol dimension is suggested-this relating to the type of aggressive offending recorded.